[dhlii]

My daughter has a 1994 E320 that aside of the typical problems has behaved pretty well for years.
Within the past year it the battery is constantly dead. We have replaced the battery twice. The alternator has been checked and is charging fine. We have checked to try to find some current draw while it is off, and can find nothing.

As it is now the car must be charged overnight atleast once a week to operate reliably.

Has anyone seen something like this ?
Anything that someone can think that I can check ?

 

[LogicalPosition]

Yes

My daughter has a 1994 E320 that aside of the typical problems has behaved pretty well for years.
Within the past year it the battery is constantly dead.
Anything that someone can think that I can check ?

Trunk light. With a fully charged battery, open the trunk after it's been closed for some time. Feel the light cover for heat. If it's warm/hot, the light is constantly ON. Probably the switch went bad.

 

[NobleTruths]

Trunk light is a good thought. Clearly there is a current draw somewhere. Can always check for amp flow across the fuses, if you are familiar with the multi-meter.

 

[LeftCoastGeek]

yeah, i'd do the fuse test with a multimeter in 10 amp mode. you remove each fuse, put the amp meter across the fuse terminals and see how much current that circuit is using. some circuits might give you a brief spike when you connect the meter, but a few seconds after connecting, no circuit should be drawing more than a small fraction of an amp, like 0.02 amps (20 milliamps). after testing one fused circuit, replace that fuse, remove the next fuse, repeat, rinse, repeat. when done, be sure to put the meter back in volts mode (or switch it off) and return the red probe to the normal socket instead of the special 10A socket.

 

[dhlii]

Thanks, her car is a wagon - but the principle is the same. We are looking for some light that is not turning off.
Thus far we have found nothing, nor can we measure any current flowing from the battery when the car is turned off.

 

[LeftCoastGeek]

last wagon I heard with this problem, turned out to be residual current drain at the rear latch motor thing.

so you lifted the battery ground cable, and put a amp meter between the battery - post and said ground cable and got zero ? huh. sure the amp meter is working? mine had a blown internal fuse which was specific to the 10 amp mode. you coudl test it with a small 12V light bulb, hook the amp meter and light bulb in series across the 12V battery (battery + to light, lamp to amp meter +, amp meter - to battery -). a 10 watt bulb will draw a little less than 1 amp (watts / volts = amps)

 

[dhlii]

I measured the current with an automotive Amp Meter connected at the positive terminal roughly as you described.
I read current when the headlights were on, but not with everything off.

But I will look at your suggestions to test. Further I have more a more sensitive DVM that can detect much smaller currents but I will have to work out how to properly connect that.

I have also tested voltage at each fuse with the fuse removed with the car turned off. The only fuses showing voltage - C & 9 are for accessories that are only powered with the car off. That does not indicate whether there is current in one of those circuits, but it should demonstrate that circuits that are supposed to be off when the car is off are actually off.

 

[nuclearseal]

I had the wagon (1989 300TE) with that same problem, pull that "C" fuse out and see how it charges up. My "C" fuse wasn't blown but it was nearly there.

I found mine by happenstance but still found it; something was drawing off the battery with the key off. After I would charge up the battery I would read 12.5v, hook up the positive cable it should read 12.5v, as soon as I hooked up the negative terminal, bam, down to 11.8v. The "C" Fuse was drawing with the key off. When the car is running are you getting the full charge off the alternator?

The fuse in the 89 is the whole back end of the car, I had the rear door lights (under the door) that stayed on which is where I think the fuse kept drawing from.

I had tried, alternator, voltage regulator, wire from alt to battery, all grounds, and it drove me nuts.

Here's my original saga http://www.benzworld.org/forums/w12...r-voltage-regulator-issue-4.html#post11750457

 

[joebagnara]

Joe

If your battery is going flat overnight and it is the usual 100 AH battery something is discharging the battery at a fairly hight value > 2 - 3 amps.
This should be able to be measured by removing the battery earth (- Neg) lead and placing your multimeter in series with this lead to earth.
If what you say actually happen I guess you will show a discharge of about 2 - 3 amps.

Next step remove fuse in order to identify offending circuit.
Work on it from there. Things like boot, glove box, security heater etc.

Could be a bad diode in the alternator if above not culprit.

Must be frustrating but best of luck.

 

[dhlii]

Been a while - and the car still has this problem.

Takes several days to draw the battery down - so the current may not be very high.
Took it to several "experts" including an auto electrical system expert and nobody could find the problem.

I have a manual disconnect on the Positive terminal - which is the only way we can keep the care from sucking the battery down if it sits for several days.
That works but it is a pain to reconnect the battery everytime you want to drive the car and disconnect everytime you return.

Separately - or related, the car goes through MASF sensors like crazy - between every 4 months and every 18 months.
MASF has been replaced several times as have air filters, etc.

When the MASF goes bad the car idles very very rough, disconnecting the MASF makes it so that it does not run so rought as to stall at stops.

Another problem is that the vehicle periodically goes into no umph mode. I think this is "limp home mode" but I am not sure.
It runs rough, it stalls easily at low speeds, it is hard to get it to shift, it can barely manage a hill, but if I can nurse it to about 40 - like find somepace going downhill with a tail wind, it will generally run better - so long as no one forces me to slow down.

When I get it home and leave it sit overnight, or sometimes on its own part way home, it will suddenly decide it is happy again.

It was suggested this could be a bad voltage regulator - which is being replaced.
And that even the dead battery could be a voltage regulator problem.
I can understand that a bad regulator could interfere with charging, but not how it could slowly dischage the batter while the car was parked.

Anyway the argument is that the "spastic mode" is because the voltage to the Car computer is too low for it to function properly.


We shall see if it behaves better after the VR is replaced.

 

[260e crusier]

Eco wiring? Has harness been replaced?

 

[LeftCoastGeek]

MASF ?

you mean the mass air flow sensor? I've never heard of HFM MAF's dying.

 

[dhlii]

Wiring harness has been replaced - more than a decade ago - this is one of those cars with the "biodegradable" wiring harness problem.

It has also been suggested that the wiring to the throttle body often fails too - and that is not replaced when the wiring harness is replaced.

I have yet to look at that. Aparently replacement throttle bodies are expensive, and I am getting really tired of rebuilding parts for old cars.

 

[dhlii]

MASF ?

you mean the mass air flow sensor? I've never heard of HFM MAF's dying.

Big black thing looks like a large plumbing T, with an electrical connector to the top.

Anyway, the car will eventually start running really rough.
When it does replacing that device will correct the rough running - for a while.

Have also replaced the filters leading to to the device.

Regardless, the MAF's are cheap, and when they fail, disconnecting it will usually make the car work well enough to get home.

The battery drain problem is a bigger deal it makes living with the car day to day unpleasant.

 

[Jayare]

dhlii

You have been a forum member for 9 yrs and posted 26 times. Zero info in your profile. Now you start asking questions by tagging a year old thread.

Start a new thread and at least mention what model the car is and what problem you're trying to resolve. Your two post above are a mess.

Jayare

Sent from my XT1080 using Tapatalk

 

[Earl.Allen]

Regardless, the MAF's are cheap, and when they fail, disconnecting it will usually make the car work well enough to get home.

HF MAF sensors for the our 1993 300CE or the TDI Jetta ARE NOT cheap; maybe your MAF supplier is the issue.

I purchased one on the cheap from Amazon and although it appeared to be OEM, it seemed to be used and was not packaged with the protective plastic covers on each end. After receiving the refund, I spent the $160 on the real real and it's been perfect since.

 

[dhlii]

This entire thread is about a single car of mine. A 1994 E320 Wagon.
It has had several problems. Others have been kind enough to provide advice.

One the rare occasions I have been able to help others, or provide information on what solved some problem of mine, I have posted that information.

I am an infrequent visitor to the forum. I have two different E320's, my life is not my car.
My Mercedes's are transportation.

Regardless, I greatly appreciate the responses I get from those who place a higher value on their mercedes.

 

[dhlii]

There are 3 cars in my "garage". But they are not public, because the forum requires uploading a picture to make them public.

 

[lowesguy]

So, my 91 SL the battery would go dead after 3-4 days, I replaced battery , checked for voltage draw, none , no lights left on etc, in the end it was the alternator, had a bad diode in it.

 

[LeftCoastGeek]

I found a power drain in my wife's wagon was from the central locking vacuum pump under the right back seat... the pressure switch in this fairly complex lock module wasn't making good contact, so the pump was running continuously. the locks still worked, which was weird. new (refurbished) CL module, all good.